Retinal architecture predicts pupillary reflex metrics in MS

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Objective To study the relation of retinal nerve fiber layer thinning to clinical and physiologic measures of visual function in patients with MS or neuromyelitis optica and unilateral optic neuropathy. Methods We studied a cohort of control subjects (n = 64) and patients (n = 24) with evidence of unilateral thinning of their average retinal nerve fiber layer as measured by optical coherence tomography in order to characterize the relationship between ganglion cell axonal degeneration and its impact upon vision and pupillary light reflex metrics using infrared pupillometry. Results When compared to the normal fellow eye, and with respect to normal subjects’ eyes, we confirmed significant abnormalities in retinal nerve fiber layer thickness, total macular volume, low-contrast letter acuity, and pupillary reflex metrics in the eye with the thinner retinal nerve fiber layer. For each −5% change in pupil diameter, there was a corresponding 7.1 µm reduction in the average retinal nerve fiber layer thickness. There was a significant difference between the pupillary metric of percent change in diameter and a decrease in low-contrast letter acuity (P < 0.001). Each −5% change in pupil diameter was associated with a substantial 3.4 line loss of low-contrast letter acuity (P < 0.001). Each −5% change in pupil diameter was associated with a 0.2 mm2 decrease in total macular volume (P < 0.001). Conclusion These findings further corroborate the hypothesis that the retina can be utilized as a model to advance our understanding of the mechanisms of axonal and neurodegeneration, and the corresponding impact of these processes upon the pathophysiology of MS and related disorders.